1. Field of the Invention
The present invention relates in general to automatic washing machines using low frequency vibration for washing clothes and, more particularly, to an improved structure in low frequency oscillating disks of such washing machines for generating of desired resonance phenomena in a multi-phase washing medium while saving energy.
2. Description of the Prior Art
In order to wash clothes in a conventional automatic washing machine using low frequency vibration, a low frequency oscillating disk placed in a washing tub generates a specified low frequency vibration which causes resonance phenomena in a multi-phase washing medium in the washing tub. Here, the multi-phase washing medium is made up of water, detergent and air. The level of low frequency is specified in accordance with the shape of the washing tub, shape of the oscillating disk and mixing ratio of the multi-phase washing medium.
In the above washing machine, the desired mechanical washing effect is achieved by the micro air bubbles generated by cavitation of the oscillating disk or nonlinear vibration. Both the cavitation and the nonlinear vibration are generated in the multi-phase medium at the same time as the generation of the resonance phenomena. The mechanical washing effect caused by the cavitation or the nonlinear vibration cooperates with a chemical washing effect caused by the detergent in the washing medium, thus to achieve the desired washing effect.
With reference to FIG. 1, there is shown a typical automatic washing machine using low frequency vibration. The washing machine generally comprises a washing tub 1, receiving multi-phase washing medium therein, and a low frequency oscillating disk 2 causing the resonance phenomena in the washing medium. The oscillating disk 2 is placed in the washing tub 1 and coupled to a disk drive actuator 3 through a shaft. The shaft transmits the drive force of the actuator 3 to the disk 2 so as to drive this disk 2.
There is provided a gap between the inner bottom of the washing tub 1 and the disk 2 for allowing the disk 2 to vertically vibrate.
In operation of the above washing machine, the low frequency oscillating disk 2 is driven by the actuator 3 in response to signals applied from an outside signal oscillator (not shown) to the actuator 3. This disk 2 thus oscillates in order to cause the resonance phenomena in the multi-phase washing medium in the washing tub 1. Here, the desired mechanical washing effect is achieved by the micro air bubbles generated by cavitation of the oscillating disk or nonlinear vibration, which cavitation and nonlinear vibration are generated in the multi-phase medium at the same time as the generation of the resonance phenomena. The above mechanical washing effect cooperates with the chemical washing effect caused by the detergent in the washing medium, thus to achieve the desired washing effect.
However, it has been noted that the above washing machine has a problem in that it uneconomically needs large amounts of energy due to the structure of its disk 2. That is, since the oscillating disk 2 is placed in the bottom of the washing tub 1 and vertically vibrates, it must be applied with hydrostatic pressure or gravitational pressure due to the weight of the washing medium when it ascends during its vertical vibration. In order to overcome the gravitational pressure, the disk 2 must use a large amount of energy in its vibration. Particularly, the disk 2 is applied with overload as it starts, so that it uses a large amount of start energy. The necessity for a large amount of energy in driving the disk 2 directly runs counter to the recent trend to save energy.